1. Field of the Invention
The present invention relates to a method for the manufacture of a phosphor pattern on a panel of a color cathode ray tube having ultra fine definition, and more particularly, to a method for preventing peeling of a black matrix (carbon stripe) using the outer surface exposure method.
2. Description of the Prior Art
For reproducing an ultra fine definition picture on a color cathode ray tube, it is necessary that the respective phosphor stripes or dots of ultra fine definition of the three primary colors be clearly separated on the phosphor screen by a black matrix as the light absorptive layers. If the separation is not perfect, the effect of mislanding of electron beams becomes strongly exhibited in the actual operating state, when various errors are considered, resulting in marked deterioration of the picture quality. Thus research has been conducted into finding a method for forming the phosphor screen having clear edges of the respective phosphors and a high packing density.
The most customary method for the manufacture of color cathode ray tubes is the so-called inner surface exposure method according to which a phosphor slurry with a pigment dispersed in a light reactive resin is coated onto a glass panel on which carbon stripes of a predetermined pattern are formed and then exposed to light through an optical mask. The non-cured portions are removed by development, and the above sequence of operations is sequentially repeated for the red, green and blue colors in the production of the stripe type color phosphor surface.
The assignee of the present invention has also proposed a so-called outer surface exposure method according to which the admixture of colors between adjoining stripes is prevented by using two kinds of photosensitive agents having differential inversion capabilities, as disclosed in Japanese Laid-open Patent Application No. 119055/1985. According to this method, the phosphor surface is prepared by coating and curing in a predetermined sequence, on the glass panel on which carbon stripes have been previously formed, a resist layer using a first sensitizer which can be inverted by aqueous hydrogen peroxide and a phosphor slurry obtained by dispersing a phosphor dyestuff in a second photosensitizer which is not inverted by hydrogen peroxide.
In the above described inner surface exposure method, the phosphor stripes are printed through an optical mask, which presents a problem because of a half shadow. In addition, due to the problem of insufficient adhesiveness between the phosphor stripes and the inner surface of the glass panel, it is difficult to form phosphor stripes having finely defined, clear edges.
In the outer surface light exposure method, the above defect of the conventional inner surface light exposure method has been eliminated but one problem remains to be solved. In the outer surface light exposure method, one inversion is caused to occur necessarily when forming the phosphor stripes of each color, so that three of the inversions are required to complete forming stripes of the three colors. However, with the repetition of the inversion of the resist layer, that is, solution and removal, the carbon stripe containing the resist layer is eroded a little by little until it is peeled off to lower the quality of the produced phosphor screen surface.